I'm pretty sure I was, if not the first, the second owner (second to David keeping one for himself) of one of David's sub chassis as I bought his prototype via a GREEDBAY auction very early in this millennium.
That being stated, I have had the pleasure of comparing it to a keel as I bought his prototype with the express purpose of comparing it to the Keel I had in my LP-12 at the time. After having done so I can say without reservation that it was indistinguishable from the real deal Keel! Regrettably I no longer have my LP-12 but if I did I would surely have purchased his PS as well to replace the Lingo 1 I had to recap (what a PITA that was) just before I sold the TT.